Recently, trace pipetting of liquid of a reagent and a sample to be used in an analysis is performed to reduce running cost. To suction trace liquid, it is necessary to grasp an accurate liquid surface height and suction liquid at a fixed position such as a liquid surface position or directly below the liquid surface position. Therefore, it is necessary to grasp the liquid surface height and accurately control a suction probe position and a liquid surface position.
Examples of a method for grasping a liquid surface height include a method for obtaining an image and information on a container containing liquid and liquid in the container by such as a camera or a laser source from the outside of the container and a method for detecting a position of a liquid surface height based on a change in a capacitance when a probe tip and a liquid surface come into contact when the suction probe is moved down in the container.
For example, PTL 1 discloses that a sample checker which irradiates a side wall of a container with a laser source to check a specimen in a blood collection tube includes a chuck mechanism for clamping and fixing the blood collection tube during irradiation of the laser source.